In the field of motion transmission by means of gear wheels there is known to use epicyclical gearings comprising a sun gear, a crown, a plurality of planet gears meshing with the sun gear and the crown and a planet gear holder, to which the planet gears are coupled by means of respective hinge pins.
Different configurations are known, in which one or more of the above said components are connected to one or more motors and to one or more users.
With the available envelope being the same for the installation of the gearing, the selection of the kind of architecture depends mainly on the load to be transmitted. As a matter of fact, as the load increases, not only do the stresses increase on the toothing of the wheels, which therefore require a dedicated surface treatment and finishing, but also the stresses on the support structures of the gear wheels such as, in particular, the hinge pins and the planet gear holders. Failures or deformations of the hinge pins or the planet gear holders generate stress concentrations and a subsequent local unpredictable wear of the various details moving one with respect to the other.
In the attempt to overcome such drawbacks, nowadays there are used wheels with a two helicoidal toothing mounted on plain bearings. If on one side such an architecture solves at least some of the above said problems, on the other side, it results poorly satisfactory in that it makes the assembly process of the gearing and the installation of the gearing on the dedicated machines particularly complicated. Besides, the two helicoidal wheel architecture requires an accurate calibration of all of the rigidities of the hinge pins of the planet gears and of the planet gear holder itself to avoid that, in a loaded condition, the toothing of the wheels is arranged in a meshing position other than the intended one and therefore operates in an excessive interference or play condition.